Thermal treatment of drying oils



- Feb. 16, 1943.

R. F. RUTHRUFF THERMAL TREATMENT OF DRYING OILS Filed Aug. 26, 19:59

IN ENT OR Patented Feb. 16, 1943- UNITED STATES PATENT i OFFICE2,310,997 THERMAL TREATMENITVOF name oms Robert F. Ruthrufl', Nutley, n.J. Application August 26, 1939, Serial No. 292,008 3 Claims.(01.166-252) This invention relates to improved methods for thethermaltreatmentof drying oils or mixtures containing drying oils. Thethermal treatment of drying oils or mixtures containing drying oils iswell known in the art. For example, lithographic varnishes are made byheating raw linseed oil or refinedlinseed oil to elevated temperaturesin the ab-' sence of air. 'During this thermal treatment a partialpolymerization and/or condensation of the drying oil occurs, theresulting product being much thicker than the original charge. .Byvarying the temperature of treatment or the time treatment or both, theextent of reaction changes and lithographic varnishes of differingconsistencies are obtained. Similarly, thermal treatment is involved inthe preparation of oleoresinous varnishes. In the preparation of thesematerials the first step usually consists in runningf the desired resinor gum or mixture thereoi, following which the heated drying oil, whichmay be either a raw drying oil, a refined drying oil, a blown dryingoil, a boiled drying oil, a drying oil that has been partiallypolymerized 1 and/or condensed, or mixtures thereof, is added.

of drying oil in the presence of air to produce blown oils, heating toproduce broken oils, et

cetera, but the processes already considered briefly are sufllcient tooutline the general aspects of the thermal treatment of drying oils andto indicate the importance of the operation.

Whenever the following terms are used in the instant description orclaims, they conform. to the respective definitions shown.

Raw drying 0iZ.A siccative oil that has been subjected to no processingprocedure except perhaps clarification.

Refined drying oil.A siccative oil that has been acid or alkali treatedor subjected to any treating procedure to improve appearance orproperties. As used in the instant specification, the term includesbroken" oils, that is, oils that have been heated to an elevatedtemperature to decompose mucilage and similar materials and thenclarified.

Blown drying oiL-A siccative oil that has been contacted with air atsuperatmospheric temperature.

Boiled drying oil-A siccative oil that has a drier or driersincorporated therein.

Lithographic varnish-A siccative oil that has been heated in thesubstantial absence of air to cause partial polymerization and/orcondensation thereof.

Running-The process of treating gums, resins, or mixtures thereof priorto adding to a drying oil or mixture of drying oils for the productionof oleoresinous varnishes, said treatment facilitating the incorporationof the gums, resins, or mixtures thereof in the siccative oil. Usuallyrunning involves melting of the gums, resins, or mixtures thereof, theoperation being accompanied by more or less distillation and thermaldecomposition of the charge.

The thermal treatment processes of the prior art have been conducted ina most inefficient manner. The processes have been operated batchwise,the thermal treatment being carried out in kettles placed over an openfire. It is evident that under such conditions control of temperature isvery diflicult and utilization of heat is quite ineflicient.Furthermore, it is impossible to avoid contamination of the product byextraneous materials, and in the event that it is desired to conduct thethermal treatment in the absence of air this is diflicult or impossibleto achieve when following the practices of the prior art. Inshort, the practices of the prior ,art in the thermal treatment ofdrying oils or mixtures containing drying oils exhibit most or all ofthe many disadvantages of batch type operations, such as non-uniformproducts, high labor costs, ineflicient utilization of utilities andequipment, et cetera.

It is an object of this invention to provide improved methods for thethermal treatment of drying oils or mixtures containing drying oils. Afurther object of this invention is to provide methods for thecontinuousthermah'treatment of drying oils or mixtures containing drying oils.Another object of this invention is to provide methods for the thermaltreatment of drying oils or mixtures containing drying oils wherebyproducts 01' uniform quality are produced. An additional object o!thisinvention is to provide methods for the etflcient utilization ofheat in the thermal treatment of drying oils or mixtures containingdrying oils. Other objects orv this invention will become evident fromthe following description.

Briefly, one embodiment of the instant invention for the thermaltreatment of drying oils or mixtures containing drying oils consists ofcontinuously passing drying ,oils or mixtures containing drying oilsthrough one or more heatin zones, transferring the thus heated charge toa combined fractionating and reaction zone, removing a portion of theliquid products from said combined t'ractionating and reaction zone forpassage to the previously mentioned heating zone or zones, passing theremainder of the liquid roducts from said combined iractionatlng andreaction zone to a secondary combined irac tionating and reaction zonepreferably operating at a lower pressure than the primary combinedfractionating and reaction zone, and removing the liquid products,comprising thermally treated product, from said secondary combinedfractionating and reaction zone.

In the instant specification, the termsprimary and secondary as appliedto the combined fractionating and reaction zones bear no relationship tothe relative importance of the elements to which the terms are applied.These terms are used for purposes of identification only and serve tofix the relative position of the elements in the whole combination.

For the more complete understanding of this invention reference is madeto the following spe= cific description, to be read in connection withthe accompanying figure forming a part of the instant specification andwherein the figure is a diagrammatic representation of one form of asuitable apparatus for the thermal treatment oi drying oils or mixturescontaining drying oils in accord with this invention.

Raw or refined linseed oil enters the system through line i and is movedby pump '2 to fur nace 3. Between pump 2 and furnace the charge ispreferably passed. through one or more heat exchangers, such as forexample coil d in the top oi tower 5 and indirect heat exchanger 6.The-furnace 3*preferably consists of a pipe still of any suitable form,many of which have been described in the art. The charge passestherethrough while confined in an elongated conduit i, which issurrounded by hot combustion gases generated by burner or burners 8. Thecharge enters furnace 8 at atmospheric pressure or superatmosphericpressure as desired and in passage through furnace 8 is heated to atemperature of 200 to 350 C. more or less, prefer= ably 250-300" C. Theheated charge leaves furnace 3 through line 9 and enters trapout tray IDin tower 5. It the charge is' at superatmospheric pressure in furnace 3,partial or complete pressure reduction may occur on passage throughvalve H in line 9.

Fractionating and reaction tower 5 may take any desired form. That shownin the figure contains a plurality of disc and doughnut trays 82, butother means for promoting liquid-vapor contact such as bubble trays,Raschig rings, or similar devices may be used. The tower shown isprovided with two trapout trays I5 and it. A closed reflux coil t and anopen reflux line it provide cooling, but other or additional cooling,means may be used as desired. Tower 5 may "also beprovided with bottomheating means if desired, for example, a closed circuit reboiler (notshown) and/or an open heating coil [5 through which steam or other hotgases may be introduced into the bottom of tower 6, the

tray HI, and this material gradually works down to lower disposedtrapout tray 13. A portion of the material in trapout tray 13 is removedthrough line H and is moved by pump l8 to line i, where it mixes withthe untreated charge, the mixture passing to furnace 3. Additionalmaterial on trapout tray I3 overflows and falls to the bottom of tower5, where it may be stripped with steam or other heated gas if desired.Bottoms from tower 5 leave through line 19 and pass through valve 2E5 tothe middle portion of fractionating and reaction tower 2|, whichoperates under subatmospherio pressure. Fractionating and reaction tower26 may take any desired form. That shown in the figure contains aplurality of disc and doughnut trays 22, but other means for promotingliquid-vapor contact such as bubble trays, Raschig rings, or similardevices may be used. The tower as shown is provided with open refluxline but other or additional cooling means maybe used if desired. Tower25 may also be provided with bottom heating means if desired, forexample, a closed circuit reboiler (not shown) and/or an open heatingcoil 25 through which steam or hot gases may be introduced into thebottom of tower the amount introduced being regulated by means of valve25. The heavier portion or" the material entering vacuum fractionatingand reaction tower 2i gradually works downward therethrough and isremoved therefrom through line 26, valve 26, and pump 2?. Material inline 26 is preferably heat exchanged with charge in indirect heatexchanger (5 and is further cooled by water or the like in indirectcooler The material removed as bottoms from tower 29 through line 25represents the desired product, consisting of polymerized and/orcondensed drying oil. It is highly desirable to clarify this finalproduct by centrifuging, filtering, or similar means (not shown) toremove certain solid decomposition products that form during theprocessing, especially when raw linseed oil is used as charge.

Flash distillate from tower 2i passes through line 29, valve 29,indirect heat exchanger 30, indirect water cooler 3i, toseparator 32.Liquid may be removed from separator 32 by line 33 and moved by pump 34to line 35. A portion of this liquid may be by-passed through line 36and valve 3'5 to storage or otherwise. Another portion may be passedthrough valve 38 and line 23 to provide open reflux in tower 2| whilethe remainder ma be sent through valve 39 in line 40, through indirectheat exchanger 30 and line H to provide open reflm in tower 5. Separator32 is connected through line H to barometric condenser 4'i or othersimilar means for maintaining a subatmospheric pressure in tower 2| andseparator 32. Any water present may be withdrawn from separator 32through line 43 and pump 48.

Overhead from tower 5 passes through line 45 and valve 46 to coolers 30and 3| and thence to separator 32.

Preferably those parts of the apparatus shown in the figure that come incontact with the heated drying oil are constructed from or lined withsuch metals and alloys as copper, aluminum, Monel metal, stainlesssteel, or the like. Steel clad with an integrally bonded lining ofstainless steel or similar non-corrosive alloy or metal provides anexcellent material of construction.

' eliminated In the production of lithographic varnishes by the methoddescribed and shown about 10 to 20% by volume of the fresh charge istaken overhead as vapors from the two towers and is eventually from thesystem through line 35 and valve 31. Theexact amount of materialeliminated as overhead depends largely upon the consistency of thelithographic varnish being produced.

It will be obvious that the method described and shown provides a.simple, convenient, and highly advantageous process for the thermaltreatment of linseed oil. In the first place, the operation iscontinuous, the drying oil being continuously added to the system whilefinished product that has been thermallytreated to the desired extent iscontinuously withdrawn therefrom. Furthermore, temperature control issimple and exact, resulting in the production of a product of thedesired and uniform properties. In addition, the thermal efiiciency ofthe system is high, the charge being preheated simultaneously in one ormore indirect heat exchangers, and additional preheat may be added tothe charge at other points if desired. Furthermore, the operating cycleis much more satisfactory than those hitherto achieved in the prior art.For example, with the method and apparatus described and pictured, oncethe unit is on stream there are no periods devoted exclusively tobringing the charge up to reaction temperature. Similarly, there are noperiods devoted exclusively to cooling the reaction products in theyard," as is necessary in processes of the prior art. With the methodand apparatus described and shown, the addition of charge, the heatingof said charge to reaction temperature, the thermal treatment of thecharge, cooling of the final product,.and withdrawal thereof all occursimultaneously. It is also obvious that with the present method andapparatus there is no chance of contaminating the product or having theproduct come in contact with air while in the heated state unless thisis desired. If it is desired to contact;the heated material with air ordilute air, however, this may be done for example by adding the gas incontrolled amounts through line 24 and valve 25 and/or line i5 and valveHi. It is obvious that the labor requirements for the improved processof this invention are at a minimum.

Another great advantage of the method forming the subject matter of theinstant invention is the extreme flexibility of the whole. As has beenmentioned previously, lithographic varnishes are made in many differentgrades, the various grades being composed of linseed oil that has beenpolycombination of said methods may be employed to vary the time or saidthermal treatment. It

'" is obvious that the time of thermal treatment may be varied bychanging the rate of introduction of drying oil charge to the systemthrough line I, other conditions being kept constant. One convenientmethod of varying the time of thermal treatment consists in maintainingthe total throughput in furnace 3 constant at all times and varying thetime oi thermal treatment by changing the relative amounts of freshdrying oil charge and material from trapout tray IS in said totalfurnace charge. For example, if the "constant total furnace throughputis set at ten volumes in unit time, when this is made up of one partfresh drying oil and nine parts material from trapout tray l3 the timeof thermal treatment is relatively long, but if, on the other hand, thetotal furnace charge con sists of nine parts raw drying oil and one partof materla1 from'trapout tray l3 the treating 1 time is relativelyshort.

Another method for changing the time and thermal treatment consists invarying the liquid level maintained in the bottom of tower 5 or thebottom of tower 2| or both. If material overfiows from trapout tray l3at a rate of one volume in unit time and the liquid maintained in thebottom of tower 5 has unit volume, the holding time will be relativelyshort. If, on the other hand, the liquid maintained in the bottom oftower 5 is equivalent to ten volumes, for example, the holding timetherein will be relatively long. The same reasoning applies to tower 2|.The method of regulating the time of thermal treating by changing theliquid level carried in the bottom of tower 5 or tower 2| or both is amost convenient one. By this method it is possible to produce alithographic varnish of practically merized and/or condensedto variousdegrees.

At constant temperature the extent of polymerization and/or condensationof a drying oil increases with increasing time at said constanttemperature. Likewise, at constant time the extent of polymerizationand/or condensation of a drying oil increases with increasing operatingtemperature. Accordingly, the extent of polymerisation and/orcondensation of a drying oil may be varied by adjusting the temperatureat which the thermal treatment occurs, the time of said treatment, orboth. When employing an apparatus similar to that shown in the figure,the

time of thermaltreatment and the temperature of saidtreatment may be setat any desired valves within wide limits.

f]. The temperature at which thermal treatment occurs is easilyregulated by adjusting the firing rate in iuma'ce 3. A number of methodsor any any desired consistency and still keep the treatv ingtemperature, fresh drying oil charging rate,

and recycle oil charging rate all constant.

Time of thermal treatment may also be varied by changingthe capacity oftrapout tray H] or trapout tray I3 or both. The effect is similar tothat described in connection with the liquid level maintained in thebottom of towers 5 and 2!. Generally, the trapout trays are fixed insize and changes are inconvenient, but if desired variable liquid leveltrapout trays, similar to those described in the prior art, may be used.It is evident that trapout tray 13 and more especially trapout tray l0are not essential for the process, these being merely convenient meansfor accomplishing a purpose. In the absence of trapout tray Hi thecharge may be added directly to a disc or doughnut in the tower. In theabsence of trapout tray I3, recycle material for the furnace may bewithdrawn directly from the bottom of the tower. While either or both ofthese trapout trays may be dispensed with, it is preferred to use bothas described and shown.

The thermal treating conditions may also be, varied by making certainminor changes in the apparatus. Among other modifications may bementioned a heating zone and two towers as shown, all of the liquidproducts from the first tower passing to the second tower, the liquidproducts from the second tower passing to storage. The first tower mayoperate at superatmospheric or atmospheric pressure, the second atreduced pressure.

Several other methods will present themselves to those skilled in theart for regulating the t me of thermal treatment, but those dealt w:' nbriefly above are suflicient to indicate ibility of the system. 7

While the method forming the subject matter of the instant invention hasbeen described with respect to the manufacture of lithographic varnishesor stand oils, the invention is of much the extreme flexwiderapplication. as will be evident to those the required fashion, isintroduced into the,

moving stream of preheated oil, for example, through line t9 and pump50, the mixture then being sent to furnace 3. If desired the requisiteamount of run material may be added subsequent to furnace 3; forexample, the material may be added-to line 9 or fractionating andreaction tower 5. The further processing is as previously explained, thetemperature of treat ment usually being equal to or somewhat lower thanis employed in the manufacture of lithographic varnishes. The finaloieoresinous varnishes are preferably clarified by any suitable means(not shown), such as filtration or centrifuging, and a drier may beadded if a boiled drying oil was not used in their formulation.

The above described processes are usually applied to linseed oil, butother drying oils can be employed if desired. For example, tung oil maybe polymerized and/or condensed by the process previously described, atemperature of 210 C. being used, the oil being held at temperature for1-2 hours. Also, very satisfactory results follow on processing amixture of tung oil and linseed oil. Other suitable drying oils ormixtures containing these may bu thermally treated by procedures andequipment already pictured and described.

From the foregoing description it is clear that the liquid productseliminated from any combined fractionating and reaction tower in unittime are equal to the total charge to said tower in unit time minus thevaporous products (if any) eliminated by said tower in unit time. Whileon stream the combined fractionating and reaction towers contain more orless liquid, which remains essentially constant throughout a run underany given set of operating conditions, addition of charge to any towerand withdrawal of liquid products and vaporousproducts (if any) from thetower being at such a rate that the amount of liquid in the towerremains essentially constant, showing neither depletion nor accumulationover the whole period of the run or any portion thereof. claims theterms withdrawing the liquid products," withdrawing a portion of theliquid products, withdrawing the remainder of the liquid products, andthe like refer to liquid products as above defined.

Although the present invention has been described in connection withdetails or specific examples thereof, it is not intended that theseshall be regarded as limitations upon the scope 01 the invention exceptinsofar as included in the accompanying claims.

I claim:

1. In a continuous process for the thermal treatment of a siccative oil,the steps including passing said oil through a heating zone wherein saidoil is brought to an elevated temperature, passing said heated oil to aprimary reaction zone, withdrawing vaporous decomposition products ofhigh volatility from said primary reaction zone through a primaryfractionation zone, withdrawing liquid products from said primaryreaction zone, passing said liquid products to a secondary reaction zoneoperating at In the appended subatmospheric pressure, withdrawingvaporous decomposition products of low volatility from said secondaryreaction zone through a secondary fractionation zone, condensing aportion of said vaporous decomposition products of low volatility andpassing them to the primary reaction zone and withdrawing liquidproducts, comprising the thermally treated product from said secondaryreaction zone.

2. In a continuous process for the thermal treatment of a siccative oil,the steps including passing said oil through a heating zone wherein saidoil is brought to an elevated temperature. passing said heated oil to aprimary reaction zone, withdrawing vaporous decomposition products ofhigh volatility from said primary reaction zone through a primaryfractionation zone, withdrawing a portion of the liquid products fromsaid primary reaction zonefpassing said portion of the liquid productsto the heating zone, withdrawing the remainder of the liquid productsfrom said primary reaction zone, passing said remainder of the liquidproducts to a secondary reaction zone operating at subatmosphericpressure, withdrawing vaporous decomposition products of low volatilityfrom said secondary reaction zone through a secondary fractionationzone, condensing a portion of said vaporous decomposition products oflow volatility and passing them to the primary reaction zone andwithdrawing liquid products, comprising the thermally treated product,from said secondary reaction zone.

3. In a continuous process for the thermal treatment of a siccative oil,the steps including passing said oil through a heating zone wherein saidoil is brought to an elevated temperature, passing said heated oil tothe upper part of a primary reaction zone, withdrawing vaporousdecomposition products of high volatility. from said primary reactionzone through a primary fractionation zone, withdrawing a portion of theliquid products from an intermediate point of said primary reactionzone, passing said portion of the liquid products to the heating zone,withdrawing the remainder of the liquid products from the lower part ofsaid primary reaction zone, passing said remainder of the liquidproducts to a secondary reaction zone operating at subatmosphericpressure, withdrawing vaporous decomposition products of low volatilityfrom said secondary reaction zone through a secondary fractionationzone, condensing a portion of said vaporous decomposition products oflow volatility and passing them to the primary reaction zone andwithdrawing liquid products, comprising the thermally treated product,from said secondary reaction zone.

ROBERT F. RUTHRUFF.

